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At least 307 records · Page 17Linked to original sources
PubMed2005

High-throughput screening of inhibitory potential of nine cytochrome P450 enzymes in vitro using liquid chromatography/tandem mass spectrometry.

The early detection of potential drug-drug interactions is an important issue of drug discovery that has led to the development of high-throughput screening (HTS) methods for potential drug interactions. We developed a HTS method for potential interactions of inhibitory drugs for nine human P450 enzymes using cocktail incubation and tandem mass spectrometry in vitro. This new method involves incubation of two cocktail doses and single cassette analysis. The two cocktail doses in vitro were developed to minimize solvent effects and mutual drug interactions among substrates: cocktail A was composed of phenacetin for CYP1A2, coumarin for CYP2A6, paclitaxel for CYP2C8, S-mephenytoin for CYP2C19, dextromethorphan for CYP2D6, and midazolam for CYP3A4; and cocktail B was composed of three substrates including bupropion for CYP2B6, tolbutamide for CYP2C9, and chlorzoxazone for CYP2E1. In the incubation study of these cocktails, the reaction mixtures were pooled and simultaneously analyzed using liquid chromatography/tandem mass spectrometry employing a fast gradient. The method was validated by comparing the inhibition data obtained from the incubation of each individual probe substrate alone with data from the new method. The IC50 value of each inhibitor in the cocktail agreed well with that of the individual probe drug as well as with values previously reported in the literature. As a HTS method for potential interactions of the inhibition of these nine P450 enzymes, this new method will be useful in the drug discovery process and for the mechanistic understanding of drug interactions.

Chromatography, Liquid↗
PubMed2003

A fluorescence-based high-throughput screening assay for inhibitors of human immunodeficiency virus-1 reverse transcriptase-associated ribonuclease H activity.

A fluorescence resonance energy transfer assay readily applicable to 96-well and 384-well microplate formats with robotic operation was developed to enable high-throughput screening for inhibitors of human immunodeficiency virus-1 (HIV-1) reverse transcriptase (RT)-associated RNase H activity, an underexplored target for antiretroviral development. The assay substrate is an 18-nucleotide 3'-fluorescein-labeled RNA annealed to a complementary 18-nucleotide 5'-Dabcyl-modified DNA. The intact duplex has an extremely low background fluorescent signal and provides up to 50-fold fluorescent signal enhancement following hydrolysis. The size and sequence of the duplex are such that HIV-1 RT-RNase H cuts the RNA strand close to the 3' end. The fluorescein-labeled ribonucleotide fragment readily dissociates from the complementary DNA at room temperature with immediate generation of a fluorescent signal. This assay is rapid, inexpensive, and robust, providing Z' factors of 0.8 and coefficients of variation of about 5%. The assay can be carried out both in real-time (continuous) and in "quench" modes; the latter requires only two addition steps with no washing and is thus suitable for robotic operation. Several chemical libraries totaling more than 106,000 compounds were screened with this assay in approximately 1 month.

Base Sequence↗
PubMed2005

Establishment of an in vitro high-throughput screening assay for detecting phospholipidosis-inducing potential.

Excessive accumulation of phospholipids results in phospholipidosis (PL), which may interfere with cellular functions, leading to acute or chronic disease or even death. Electron-microscopic detection of cytoplasmic lamellar bodies is often used as a diagnostic criterion of PL, but a faster, more convenient procedure is required for high-throughput assay of the PL-inducing potential of candidate drugs. We have developed a 96-well microplate cell-culture method for detecting PL, using a phosphatidylcholine-conjugated dye (NBD-PC) and a fluoro-microplate reader. The fluorescence intensity due to NBD-PC was normalized to that of Hoechst33342, used as an indicator of cell number, to obtain the amount of NBD-PC taken up per living cell. To select a suitable cell type, we examined the PL-detection sensitivity of five cell lines, as well as human and rat primary hepatocyte cultures, with five cationic amphiphilic drugs (CAD) as PL inducers and a negative control compound. The cell lines CHO-K1 and CHL/IU gave the best results. The NBD-PC uptake per CHO-K1 cell showed a high correlation with the pathological score of PL for 24 compounds, including PL-positive and negative compounds. This high-throughput screening assay for PL-inducing potential (HTS-PL assay) offers high sensitivity and accuracy, and it allows simultaneous determination of cytotoxicity.

4-Chloro-7-nitrobenzofurazan↗
PubMed2006

Inhibition profiling of human carbonic anhydrase II by high-throughput screening of structurally diverse, biologically active compounds.

Human carbonic anhydrase II (CA II), a zinc metalloenzyme, was screened against 960 structurally diverse, biologically active small molecules. The assay monitored CA II esterase activity against the substrate 4-nitrophenyl acetate in a format allowing high-throughput screening. The assay proved to be robust and reproducible with a hit rate of approximately 2%. Potential hits were further characterized by determining their IC(50) and K(d) values and tested for nonspecific, promiscuous inhibition. Three known sulfonamide CA inhibitors were identified: acetazolamide, methazolamide, and celecoxib. Other hits were also found, including diuretics and antibiotics not previously identified as CA inhibitors, for example, furosemide and halazone. These results confirm that many sulfonamide drugs have CA inhibitory properties but also that not all sulfonamides are CA inhibitors. Thus many, but not all, sulfonamide drugs appear to interact with CA II and may target other CA isozymes. The screen also yielded several novel classes of nonsulfonamide inhibitors, including merbromin, thioxolone, and tannic acid. Although these compounds may function by some nonspecific mechanism (merbromin and tannic acid), at least 1 (thioxolone) appears to represent a genuine CA inhibitor. Thus, this study yielded a number of potentially new classes of CA inhibitors and preliminary experiments to characterize their mechanism of action.

Carbonic Anhydrase II↗
PubMed2005

Synthesis and chemiluminescent high throughput screening for inhibition of acetylcholinesterase activity by imidazo[2,1-b]thiazole derivatives.

The synthesis of a new series of imidazo[2,1-b]thiazole derivatives is described. They were tested as acetylcholinesterase inhibitors by means of a chemiluminescent method suitable for high throughput screening. The compounds without quaternization had no appreciable inhibitory potency probably because they are poorly soluble in water. The corresponding quaternized compounds were good inhibitors with activity related to the spacer employed.

Acetylcholinesterase↗
PubMed2001

Aptamers as reagents for high-throughput screening.

The identification of new drug candidates from chemical libraries is a major component of discovery research in many pharmaceutical companies. Given the large size of many conventional and combinatorial libraries and the rapid increase in the number of possible therapeutic targets, the speed with which efficient high-throughput screening (HTS) assays can be developed can be a rate-limiting step in the discovery process. We show here that aptamers, nucleic acids that bind other molecules with high affinity, can be used as versatile reagents in competition binding HTS assays to identify and optimize small-molecule ligands to protein targets. To illustrate this application, we have used labeled aptamers to platelet-derived growth factor B-chain and wheat germ agglutinin to screen two sets of potential small-molecule ligands. In both cases, binding affinities of all ligands tested (small molecules and aptamers) were strongly correlated with their inhibitory potencies in functional assays. The major advantages of using aptamers in HTS assays are speed of aptamer identification, high affinity of aptamers for protein targets, relatively large aptamer-protein interaction surfaces, and compatibility with various labeling/detection strategies. Aptamers may be particularly useful in HTS assays with protein targets that have no known binding partners such as orphan receptors. Since aptamers that bind to proteins are often specific and potent antagonists of protein function, the use of aptamers for target validation can be coupled with their subsequent use in HTS.

Animals↗
PubMed1999

A solid-phase glycosyltransferase assay for high-throughput screening in drug discovery research.

Glycosyltransferases mediate changes in glycosylation patterns which, in turn, may affect the function of glycoproteins and/or glycolipids and, further downstream, processes of development, differentiation, transformation and cell-cell recognition. Such enzymes, therefore, represent valid targets for drug discovery. We have developed a solid-phase glycosyltransferase assay for use in a robotic high-throughput format. Carbohydrate acceptors coupled covalently to polyacrylamide are coated onto 96-well plastic plates. The glycosyltransferase reaction is performed with recombinant enzymes and radiolabeled sugar-nucleotide donor at 37 degrees C, followed by washing, addition of scintillation counting fluid, and measurement of radioactivity using a 96-well beta-counter. Glycopolymer construction and coating of the plastic plates, enzyme and substrate concentrations, and linearity with time were optimized using recombinant Core 2 beta1-6-N-acetylglucosaminyltransferase (Core 2 GlcNAc-T). This enzyme catalyzes a rate-limiting reaction for expression of polylactosamine and the selectin ligand sialyl-Lewis(x) in O-glycans. A glycopolymer acceptor for beta1-6-N-acetylglucosaminyltransferase V was also designed and shown to be effective in the solid-phase assay. In a high-throughput screen of a microbial extract library, the coefficient of variance for positive controls was 9.4%, and high concordance for hit validation was observed between the Core 2 GlcNAc-T solid-phase assay and a standard solution-phase assay. The solid-phase assay format, which can be adapted for a variety of glycosyltransferase enzymes, allowed a 5-6 fold increase in throughput compared to the corresponding solution-phase assay.

Acrylic Resins↗
PubMed2005

Human immunodeficiency virus type 1 latency model for high-throughput screening.

Human immunodeficiency virus type 1 (HIV-1) is not eliminated from patients even after years of antiretroviral therapy, apparently due to the presence of latently infected cells. Here we describe the development of a cell-based system of latency that can be used for high-throughput screening aimed at novel drug discovery to eradicate HIV-1 infection.

Anti-HIV Agents↗
PubMed2005

High-throughput screening of protein binding by equilibrium dialysis combined with liquid chromatography and mass spectrometry.

A new approach for screening plasma protein binding is presented. The method is based on equilibrium dialysis combined with rapid generic LC-MS bioanalysis by using a sample pooling approach enabling high-throughput screening of protein binding in the drug discovery phase. The method is evaluated by a comparison of measured unbound free fractions f(u) (%) between single and pooled compounds for a test set of structurally diverse compounds with a wide range of unbound fractions. Test compounds include 1 acidic and 10 basic drug standards along with 36 new chemical entities. A good correlation (R2>0.95) of f(u) (%) between the single and pooled compounds is found, suggesting that at least 10 compounds can be simultaneously measured with acceptable accuracy. A simplified drug-protein binding model is applied to calculate the f(u) (%) of drugs at various drug and protein concentrations and this is applied to elucidate the applicability of the sample pooling approach from a theoretical standpoint. Moreover, pH shifts in the plasma were observed after dialysis when using different types of buffers and the impact of that on the f(u) is illustrated in association with their physicochemical properties, in particular the ionization state of compounds by the profile of effective mobility as a function of pH. A new buffer is proposed being able to minimize the pH shift of plasma during the dialysis. In addition, the application of the proposed buffer does not necessarily require adjusting plasma pH before the dialysis and utilizing a CO2 incubator during the dialysis. The effect of the ionic strengths of different buffers on MS signals is investigated with regard to ion suppression. The sample pooling method not only significantly reduces the plasma volume required but also the number of bioanalysis samples as compared to the single compound measurements by a conventional approach. The new proposed approach is especially beneficial for measuring in vitro protein binding in matrices such as mouse plasma where plasma is available only in limited amounts. The current new development will facilitate the drug discovery process by more rapidly assessing the protein binding potential of drug candidates.

Animals↗
PubMed2000

Identification of mRNAs expressed in tumor-infiltrating lymphocytes by a strategy for rapid and high throughput screening.

Most gene expression methods often involve cumbersome steps or use expensive facilities. Additionally, some of the techniques, such as cDNA biochip, cannot define the sub-population of tissue from which the amplified cDNA was made. Here we present a rapid and high throughput screening method for analyzing the pattern of gene expression of tumor-infiltrating lymphocyte (TIL), which can minimize manipulations in cloned DNA sequencing and in bioinformatics. The pattern of TIL gene expression was studied in one ovarian cancer and one liver cancer. Our results have demonstrated that TILs have three different gene expression profiles: the first set of genes is involved in cell proliferation and mitogenic stimulation, such as c-myc and IL-8, LD78, MIP-1beta, insulin-induced protein and AH-receptor; the second set of genes includes those involved in attachment of lymphocytes to endothelium and extravasation into tumor tissues such as P-selectin ligand and integrin; and the third set, which includes genes such as the perforin, FAS ligand and granzyme B, is related to cytotoxic function to tumor cells. The patterns of TIL gene expression obtained from two specimens are marginally different and can be used in explaining the basis of molecular mechanisms regulating cellular interactions and cytotoxicity.

Computational Biology↗
PubMed2002

A high throughput screening assay to screen for CYP2E1 metabolism and inhibition using a fluorogenic vivid p450 substrate.

Large-scale screening of multiple compound libraries and combinatorial libraries for pharmacological activity is one of the novel approaches of the modern drug discovery process. The application of isozyme-specific high-throughput screening (HTS) assays for characterizing the interactions of potential drug candidates with major human drug-metabolizing cytochrome p450 enzymes (p450s) is newly becoming an essential part of this process. Fluorescence-based HTS assays have been successfully employed for in vitro assessment of drug-drug interactions and enzyme inhibition with several p450 isoforms, including CYP3A4, CYP2D6, CYP2C9, and CYP2C19. Here we describe a fluorescence-based HTS assay for detecting drug metabolism and inhibition with human CYP2E1. CYP2E1 plays an important role in the metabolism of several drugs, many solvents, and toxins and therefore has been repeatedly linked to numerous pathologies, including cancer, liver and kidney toxicity, diabetes, and alcoholism. The assay is based on the ability of a drug to compete with the fluorogenic Vivid CYP2E1 Blue Substrate for CYP2E1 metabolism and thus enables rapid screening of lead molecules for their inhibitory potential. We have used this assay to screen a panel of drugs and compounds for their effects on CYP2E1 metabolism and inhibition. Our results demonstrate the assay's usefulness in identifying CYP2E1 substrates and inhibitors and in enabling in-depth characterization of their interactions with the CYP2E1 isozyme. We also present detailed characteristics of the assay, including its dynamic range and Z'-factor values, which indicate that this robust assay is well suited for kinetic and inhibition studies in HTS formats.

Baculoviridae↗
PubMed2001

Detection of a decrease in green fluorescent protein fluorescence for the monitoring of cell death: an assay amenable to high-throughput screening technologies.

BACKGROUND: Reliable assessment of cell death is now pivotal to many research programs aiming at generating new anti-tumor compounds or at screening cDNA libraries. Such approaches need to rely on reproducible, easy-to-handle, and rapid microplate-based cytotoxicity assays that are amenable to high-throughput screening (HTS) technologies. We describe a method for the direct measurement of cell death, based on the detection of a decrease in fluorescence observed following death induction in cells expressing enhanced green fluorescent protein (EGFP). METHODS: Cell death was induced by a variety of apoptotic stimuli in various EGFP-expressing mammalian cell lines, including those routinely used in anti-cancer drug screening. Decrease in fluorescence was assessed either by flow cytometry (and compared with other apoptotic markers) or by a fluorescence microplate reader. RESULTS: Cells expressing EGFP exhibited a decrease in fluorescence when treated by various agents, such as chemotherapeutic drugs, UV irradiation, or caspase-independent cell death inducers. Kinetics and sensitivity of this EGFP-based assay were comparable to those of traditional apoptosis markers such as annexin-V binding, propidium iodide incorporation, or reactive oxygen species production. We also show that the decrease in EGFP fluorescence is directly quantifiable in a fluorescence-based microplate assay. Furthermore, analysis of EGFP protein content in cells undergoing cell death demonstrates that the decrease in fluorescence does not arise from degradation of the protein. CONCLUSIONS: This novel GFP-based microplate assay combines sensitivity and rapidity, is easily amenable to HTS setups, making it an assay of choice for cytotoxicity evaluation.

3T3 Cells↗
PubMed2004

Gene expression-based high-throughput screening(GE-HTS) and application to leukemia differentiation.

Chemical genomics involves generating large collections of small molecules and using them to modulate cellular states. Despite recent progress in the systematic synthesis of structurally diverse compounds, their use in screens of cellular circuitry is still an ad hoc process. Here, we outline a general, efficient approach called gene expression-based high-throughput screening (GE-HTS) in which a gene expression signature is used as a surrogate for cellular states, and we describe its application in a particular setting: the identification of compounds that induce the differentiation of acute myeloid leukemia cells. In screening 1,739 compounds, we identified 8 that reliably induced the differentiation signature and, furthermore, yielded functional evidence of bona fide differentiation. The results indicate that GE-HTS may be a powerful, general approach for chemical screening.

Acute Disease↗
PubMed2003

Chiral liquid chromatography-mass spectrometry for high-throughput screening of enzymatic racemase activity.

In finding suitable biocatalysts for processes in chemical industry, expression libraries are constructed containing typically >10,000 clones. Search for a desired activity is done by examination of all the clones in one or more libraries using a high-throughput screening assay. Here we describe a method for the screening of the enzymatic racemase activity of clones from an expression library on alpha-amino-epsilon-caprolactam (ACL) using a fast chiral LC separation and ionspray-MS as the detection technique. After substrate incubation with S-ACL, the 96-well microplates were centrifuged to remove cell material. The conversion of S-ACL to R-ACL was monitored by quantitation of the R-ACL enantiomer. Separation of the two ACL enantiomers was performed on a Crownpak CR+ column within 1 min. A Gilson 215 autosampler with a 889 multiple injection probe was used for injecting the samples into the LC system. The total analysis time for a 96-well microplate was 56 min. The MS was operated in the positive-ion mode using selected ion monitoring at m/z 129 [M+H]+ of ACL. Using this method over 12,000 samples were analyzed without loss in performance of the system. The LC column remained stable without loss of resolution and the MS system did not show loss in sensitivity throughout the screening. Inter-day reproducibility was within 15%.

Amino Acid Isomerases↗
PubMed2005

Structural dissection and high-throughput screening of mannosylglycerate synthase.

The enzymatic transfer of activated mannose yields mannosides in glycoconjugates and oligo- and polysaccharides. Yet, despite its biological necessity, the mechanism by which glycosyltransferases recognize mannose and catalyze its transfer to acceptor molecules is poorly understood. Here, we report broad high-throughput screening and kinetic analyses of both natural and synthetic substrates of Rhodothermus marinus mannosylglycerate synthase (MGS), which catalyzes the formation of the stress protectant 2-O-alpha-D-mannosyl glycerate. The sequence of MGS indicates that it is at the cusp of inverting and retaining transferases. The structures of apo MGS and complexes with donor and acceptor molecules, including GDP-mannose, combined with mutagenesis of the binding and catalytic sites, unveil the mannosyl transfer center. Nucleotide specificity is as important in GDP-D-mannose recognition as the nature of the donor sugar.

Crystallography↗
PubMed2005

A short-incubation reporter-gene assay for high-throughput screening of estrogen receptor-alpha antagonists.

Estrogen receptor (ER) alpha and beta are ligand-activated nuclear transcription factors that mediate the effects of the steroid hormone 17beta-estradiol. Tissue-selective ER modulators have been developed for the treatment of a variety of diseases, including osteoporosis and hormone-dependent breast cancer. Second- and third-generation selective ER modulators are in development, with the goal of reducing toxicity and improving tissue-selective efficacy. Novel tissue-selective and ERsubtype specific ligands may have the potential of providing a new paradigm for maintaining the health of women. The traditional cell-based screening assays for nuclear receptors require 16-18 h of incubation, which limits the assay miniaturization for ultra-high-throughput screening. We have developed a new cell-based ERalpha transactivation assay for the screening of ERalpha-specific antagonists with only 4 h of incubation time. The assay was optimized and used for a fully automated ultrahigh-throughput screen in 3,456-well nanoplate format. The screening throughput was 250,000-300,000 compounds per day, and a number of valuable leads were identified.

Animals↗
PubMed2006

A cell-based ultra-high-throughput screening assay for identifying inhibitors of D-amino acid oxidase.

Enzymes are often considered less "druggable" targets than ligand-regulated proteins such as G-protein-coupled receptors, ion channels, or other hormone receptors. Reasons for this include cellular location (intracellular vs. cell surface), typically lower affinities for the binding of small molecules compared to ligand-specific receptors, and binding (catalytic) sites that are often charged or highly polar. A practical drawback to the discovery of compounds targeting enzymes is that screening of compound libraries is typically carried out in cell-free activity assays using purified protein in an inherently artificial environment. Cell-based assays, although often arduous to design for enzyme targets, are the preferred discovery tool for the screening of large compound libraries. The authors have recently described a novel cell-based approach to screening for inhibitors of a phosphatase enzyme and now report on the development and implementation of a homogeneous 3456-well plate assay for D-amino acid oxidase (DAO). Human DAO was stably expressed in Chinese hamster ovary (CHO) cells, and its activity was measured as the amount of hydrogen peroxide detected in the growth medium following feeding the cells with D-serine. In less than 12 weeks, the authors proved the concept in 96-and then 384-well formats, miniaturized the assay to the 3456-well (nanoplate) scale, and screened a library containing more than 1 million compounds. They have identified several cell-permeable inhibitors of DAO from this cell-based high-throughput screening, which provided the discovery program with a few novel and attractive lead structures.

Animals↗
PubMed2004

Identification of synthetic endothelial cell-specific promoters by use of a high-throughput screen.

Transcriptional targeting is a desirable property for many gene transfer applications. Because endothelial cells line most blood vessels, they are attractive candidates for the introduction of therapeutic gene products. As a proof-of-concept study, we attempted to identify a synthetic, endothelial cell-specific promoter by use of a high-throughput screen involving self-inactivating (SIN) human immunodeficiency virus type 1 (HIV-1)-based vectors. Select duplex oligodeoxynucleotides recognized by transcription factors and located 5' of endothelial cell-specific mRNA transcripts were randomly ligated and cloned upstream of a minimal ICAM-2 promoter driving enhanced green fluorescent protein (eGFP) in a SIN HIV-1-based vector. Vesicular stomatitis virus G protein-pseudotyped particles were prepared from a library of >10(6) vector recombinants and used to transduce an endothelial cell line. The highest eGFP expressers were repeatedly sorted, and the synthetic promoters were recovered and retested by a luciferase reporter. Several promoters were active and specific to endothelial cells of varied species, with high selectivity indexes and inducibility under hypoxia-mimetic conditions. One in particular was then introduced back into a SIN HIV-1-based vector to confirm its endothelial cell activity and specificity. This study suggests that SIN vectors may be used in a high-throughput manner to identify tissue-specific promoters of high activity, with potential applications for both transcriptional targeting and gene transfer.

Antigens, CD↗